An integrated payload design for the Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL)

ARIEL (the Atmospheric Remote-sensing Infrared Exoplanet Large-survey) is one of the three candidates for the next ESA medium-class science mission (M4) expected to be launched in 2026. This mission will be devoted to observing spectroscopically in the infrared a large population of warm and hot transiting exoplanets (temperatures from similar to 500 K to similar to 3000 K) in our nearby Galactic neighborhood, opening a new discovery space in the field of extrasolar planets and enabling the understanding of the physics and chemistry of these far away worlds. The three candidate missions for M4 are now in a Phase A study which will run until mid-2017 at which point one mission will be selected for implementation. ARIEL is based on a 1-m class telescope feeding both a moderate resolution spectrometer covering the wavelengths from 1.95 to 7.8 microns, and a four channel photometer (which also acts as a Fine Guidance Sensor) with bands between 0.55 and 1.65 microns. During its 3.5 years of operation from an L2 orbit, ARIEL will continuously observe exoplanets transiting their host star. This paper presents the overall view of the integrated design of the payload which is proposed for this mission. It tightly integrates the various payload elements in order to allow the exacting photometric stability targets to be met while providing simultaneous spectral and photometric data from the visible to the mid-infrared. We identify and discuss the key requirements and technical challenges for the payload and address the trade-offs that we are undertaking. We will show how we will produce a fully integrated and calibrated payload for ARIEL that can be built within the mission and programmatic constraints and will meet the challenging scientific performance required for transit spectroscopy.